HOUSTON (AP) — Despite the miles traveled, the tens of millions of dollars raised and the ceaseless churn of policy papers, the Democratic primary has been remarkably static for months with Joe Biden leading in polls and Elizabeth Warren and Bernie Sanders vying to be the progressive alternative. That stability is under threat on Thursday.

All of the top presidential candidates will share a debate stage, a setting that could make it harder to avoid skirmishes among the early front-runners. The other seven candidates, meanwhile, are under growing pressure to prove they’re still in the race to take on President Donald Trump next November.

The debate in Houston comes at a pivotal point as many voters move past their summer vacations and start to pay closer attention to the campaign. With the audience getting bigger, the ranks of candidates shrinking and first votes approaching in five months, the stakes are rising.

“For a complete junkie or someone in the business, you already have an impression of everyone,” said Howard Dean, who ran for president in 2004 and later chaired the Democratic National Committee. “But now you are going to see increasing scrutiny with other people coming in to take a closer look.”

The debate will air on a broadcast network with a post-Labor Day uptick in interest in the race, almost certainly giving the candidates their largest single audience yet. It’s also the first debate of the 2020 cycle that’s confined to one night after several candidates dropped out and others failed to meet new qualification standards.

If nothing else, viewers will see the diversity of the modern Democratic Party. The debate, held on the campus of historically black Texas Southern University, features several women, people of color and a gay man, a striking contrast from the increasingly white and male Republican Party. It will unfold in a rapidly changing state that Democrats hope to eventually bring into their column.

Perhaps the biggest question is how directly the candidates will attack one another. Some fights that were predicted in previous debates failed to materialize with candidates like Sanders and Warren in July joining forces to take on their rivals.

The White House hopefuls and their campaigns are sending mixed messages about how eager they are to make frontal attacks on anyone other than President Donald Trump. That could mean the first meeting between Warren, the rising progressive calling for “big, structural change,” and Biden, the more cautious but still ambitious establishmentarian, doesn’t define the night. Or that Kamala Harris, the California senator, and Pete Buttigieg, the mayor of South Bend, Indiana, look to reclaim lost momentum not by punching upward but by reemphasizing their own visions for America.

Biden, who has led most national and early state polls since he joined the field in April, is downplaying the prospects of a titanic clash with Warren, despite their well-established policy differences on health care, taxes and financial regulation.

“I’m just going to be me, and she’ll be her, and let people make their judgments. I have great respect for her,” Biden said recently as he campaigned in South Carolina.

Warren says consistently that she has no interest in going after Democratic opponents.

Yet both campaigns are also clear that they don’t consider it a personal attack to draw sharp policy contrasts. Warren, who as a Harvard law professor once challenged then-Sen. Biden in a Capitol Hill hearing on bankruptcy law, has noted repeatedly that they have sharply diverging viewpoints. Her standard campaign pitch doesn’t mention Biden but is built around a plea that the “time for small ideas is over,” an implicit criticism of more moderate Democrats who want, for example, a public option health care plan instead of single-payer or who want to repeal Trump’s 2017 tax cuts but not necessarily raise taxes further.

Biden, likewise, doesn’t often mention Warren or Sanders. But he regularly contrasts the price tag of his public option insurance proposal to the single-payer system that Warren and Sanders back. The former vice president, his aides say, is willing to have discussion over health care, including with Warren.

Ahead of the debate, the Biden campaign also emphasized that he’s released more than two decades of tax returns, in contrast to the president. That’s a longer period than Warren, and it could reach back into part of her pre-Senate career when she did legal work that included some corporate law.

Biden’s campaign won’t say that he’d initiate any look that far back into Warren’s past, but in July, Biden was ready throughout the debate with specific counters for rivals who brought up weak spots in his record.

There are indirect avenues to chipping away at Biden’s advantages, said Democratic consultant Karen Finney, who advised Hillary Clinton in 2016. Finney noted Biden’s consistent polling advantages on the question of which Democrat can defeat Trump.

A Washington Post-ABC poll this week found that among Democrats and Democratic-leaning voters, Biden garnered 29% support overall. Meanwhile, 45% thought he had the best chance to beat Trump, even though just 24% identified him as the “best president for the country” among the primary field.

“That puts pressure on the others to explain how they can beat Trump,” Finney said.

Voters, Finney said, “want to see presidents on that stage,” and Biden, as a known quantity, already reaches the threshold. “If you’re going to beat him, you have to make your case.”

Some candidates say that’s their preferred path.

Harris, said spokesman Ian Sams, will “make the connection between (Trump’s) hatred and division and our inability to get things done for the country.”

Buttigieg, meanwhile, will have an opportunity to use his argument for generational change as an indirect attack on the top tier. The mayor is 37. Biden, Sanders and Warren are 76, 78 and 70, respectively — hardly a contrast to the 73-year-old Trump.

There’s also potential home state drama with two Texans in the race. Former Rep. Beto O’Rourke and former Obama housing secretary Julian Castro clashed in an earlier debate over immigration. Castro has led the left flank on the issue with a proposal to decriminalize border crossings.

For O’Rourke, it will be the first debate since a massacre in his hometown of El Paso prompted him to overhaul his campaign into a forceful call for sweeping gun restrictions, complete with regular use of the F-word in cable television interviews.

O’Rourke has given no indication of whether he’ll bring the rhetorical flourish to broadcast television.

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